Automatic fluid fuel burner control



Jan. 6, 1942. s. J. LEVINE I AUTOMATIC FLUID FUEL BURNER CONTROL FiledJuly 31. 1940 PILOT BURNER HNN BURNER Inventor: Samuel J. Levine,

y His Attorney Patented Jan. 6, 1942 v i I UNITED STATES PATENT OFFICEAUTOMATIC FLUm FUEL BURNER CQNTROL Samuel J. Levine, Verona, N. .L,assignor to General Electric Company, a corporation of New YorkApplication July 31,1940, Serial N... 348,949

Claims. (Cl. 158117.1)

This invention relates to a control system for a call for heat by acontrol device and to embody a fluid fuel burner of the type having amain into such a system safety control features which burner and anormally out pilot burner for ignitwill give more complete protectionagainst the ing the main burner, an igniter, motor-operated escape oflarge quantities of unburned fuel and valves for controlling the mainburner and pilot 5 the resultant danger of explosion upon the ocburner,and a relay switching system for concurrence of abnormal operatingconditions.

trolling the operation of the main burner and More specifically, it isan object of my invenpilot burner valve motors. In this type of controltion to provide a control system for afluid fuel system'it is common toprovide a combustion reburner adapted to prevent the escape of unburnedsponsive device associated with the pilot burner fuel from the mainburner in the event of pilot which operates a control device to preventthe gas failure, pilot flame failure, or igniter failure energization ofthe main burner valve until comcaused by abnormal operating conditionsincludbustion occurs at the pilot burner. This is acing momentary dipsin fuel pressure-and electricomplished by connecting the control deviceto cal supply voltage.

energize the pilot burner in the start" position It is a further objectof myinvention to proand the main 'burner in the run position. This videa control system of the type described which prevents the possibility ofa large quantity of unwill be positive in operation, give a maximum ofburned fuel from escaping from the main burner protection and which willbe cheap to manufacand the resultant danger of explosion in case tureand install.

the pilot burner should fail to ignite for some m Further objects andadvantages of my invenreason dining the starting operation of the tionwill become apparent as the following deburner. It has been found,however, that these scription proceeds, and the features of noveltycombustion responsive devices do not give comwhich characterize my inv nw e Pointed plete protection upon the occurrenceof certain outwith'particularity in the'claims annexed to abnormal conditions. Forexample, assume that and forming a part of this specification.

the burner is running normally and the main 1 My invention will bebetter understood from I burner is energized. The fuel pressure may thenthe following description taken in connection with dip sufliciently toput out the pilot and main the accompanying drawing, in which the singleburner and then immediately return to normal. figure illustrates, inschematic form, one embodi- Due to the fact that the combustionresponsive 3i ment of my invention.

devices often used, such as one. of the thermal Referring now to thedrawing, the main burner type, require a considerable time to return tothe II of a fluid fuel burner, illustrated only schestart" position upona cessation of combustion, matically, is supplied with fluid fuelthrough a a large quantity of unburned fuel may escape conduit llconnectedtothe inlet conduit l2 which before the main burner isdeenergized. is connected to any suitable source of fluid fuel Likewise,in systems using electrically operated not shown. The conduit H isprovided with a motors to open the control valves, a sudden dip normallyclosed valve l8 operated by any suitable in supply voltage duringoperation of the main electrical actuating means such as a solenoid mo-.burner may cause the valves to drop closed for a tor ll. The pilotburner I! is supplied withfuel sufiicient time to put out the pilot andmain throushaconduit whichis connected with the burner but thenimmediately open them upon a fuel supply conduit II. The pilot burnerconreturn of the voltage to normal. Here again a duit I is likewiseprovided with a normally closed large quantity of unburned fuel mayescape from valve I! operated by a Suit ble el tric l ctu tthe mainburner before the combustion responing means such as a solenoid motorl8. sive device can return to the start position The pilot burner is ofthe normally out yp and deenergize the main. burner. Also, in controlthat is, the pilot burner is on only when the circuits where the valvemotors are energized burner is in operation. This arrangement of thethrough a circuit including a control switch such pilot burner isdesirable because of the saving as a thermostat, a manual manipulationof the in fuel cost butsom'e me ns m be Pr v thermostat has the sameeffect on the system as M for lighting pilot burner when the burner isavoltage dip described above. started. To accomplish this I haveprovided It is an object of my invention to provide an an electricigniter I! of the hot wire type the automatic control system for a fluidfuel burner connections of which will be described below. It

which will automatically control the operation of is obvious that otherwell-known types of electric the pilot burner and main burner inresponse to isniters, a platinum sponge, or a constantly burn- A trolledby any suitable combustion responsive device 22. I have shown at 22 acombustion responsive device of the thermal type comprising athermostatic bulb 23, located adjacent'the pilot burner l5, connected toa Sylphon bellows 24 by a tube 25. The bulb 23 is located so that it isnot appreciably afl'ected by the heat generated by the igniter l9. TheSylphon bellows operates the switching means 2|through a member 26. Anyother suitable form of combustion responsive device might be used tooperate the switching means 2|.

The valve motors l4 and I3 and the igniter |9 are supplied withelectrical energy from the secondary winding 30 of the transformer 28having its primary winding 29 connected to a suitable source 21. Themotors l4, l8, and igniter |9 are controlled by switching means theaction of which will now be described.

In the drawing the control apparatus is shown in the "off position. Whenthe control switch 20 is closed such as by the movement of the bimetalmember 33 of a thermostat to the left closing contacts 3|, 32 inresponse to a call for heat in a zone heated by the burner, the pilotvalve motor and igniter are energized through the switching means 2|.valve motor may be traced from the secondary 30 of the transformer 28through line 34, thermostat 28, line 36; contact 31-a, bridging member31, contact 31b, line 40, pilot valve motor |8. line 35 back tosecondary 30. The circuit to the igniter may be traced from secondary 38to contact 31b as described above, line 4|, contact 38-b, bridgingmember 38, contact 38a, line 42, igniter l9, line 35 back to secondary30. The pilot valve motor being energized the valve I1 is opened andfuel is discharged from the pilot burner l and lighted by the energizedigniter I9.

It will be noted that I have provided a holding circuit around contacts31-a, 31-b, controlled by a switch 43. The switch 43 is actuated inresponse to a predetermined fuel pressure in the pilot burner conduitl6. To accomplish this I have illustrated the switch 43 connected by amember 45 to a diaphragm 44 movable in response to the pressure. inchamber 46. The chamber 46 is connected to conduit l6 through a tube 41.When pilot valve |1 opens, the pressure in conduit I6, and consequentlychamber 46, increases forcingdiaphragm 44 upwardly thereby closingswitch 43. The switch 43, when closed, shorts out the current paththrough bridging member 31 of switch 2|. The switch is arranged to openwhen the fuel pressure in conduit decreases to a value slightly greaterthan that required to maintain combustion at the pilot burner. Thus theswitch 43 will open the electrical circuit before the pressure inconduit I6 is reduced to a point where the pilot will go out or is soreduced in size that it will not ignite the fuel issuing from the mainburner.

After combustion starts at the pilot burner I5 75 niter.

The circuit to the pilot.

the fluid in thermostatic bulb 23 becomes heated and expands causing theSylphon bellows to move upwardly thereby causing the bridging members31, 38, and 39 of switch 2| to move to the run" position indicated bythe dotted lines. The opening of the contacts 31-a, 31-b has no effecton the control circuit since the energizing current passes through theholding circuit closed by switch 43. However, the opening of contacts38a, 38-11 breaks the circuit to the igniter thereby deenergizing thesame. The closing of contacts 39-a, 39-11, by the bridging member 39completes the circuit to energize the main burner valve motor l4 therebycausing the opening of the valve and a flow of fuel to the main burnerwhich is then ignited by the pilot burner. The circuit to the main valvemotor |4 may then be traced from the transformer secondary 38 throughline 34, thermostat 23, line 36, switch 43, lines 40 and 4|, contact39b, bridging member 39, contact 39-a, line 41, solenoid motor 4 andline 35 back to transformer secondary 39.

When the thermostat 28 is satisfied the contacts 3|, 32 opendeenergizing the pilot burner and main burner valve motors l8 and I4 andallowing the valves l1 and I3 to close thus turnin 01! the burners.valve |1 causes an immediate decrease of the pressure in conduit l6 andhence pressure chamber 46 thereby causing switch 43 to open.Subsequently the thermostatic bulb 23 cools down and gradually theSylphon bellows contracts causing the bridging members 31, 38, and 39 ofswitch 2| to return to the start position. The control apparatus is thenready for another cycle of operation. a

The operation of my control system may be summarized as follows:

Upon the closing of the control switch or thermostat 20 the pilot valveI1 is opened its motor |8 being energized through switch member 31. Theigniter I3 is also heated being energized through switch members 31 and38. As soon as pilot valve l1 opens, switch 43 closes since the gaspressure builds up a chamber 46. When the igniter reaches sufllcienttemperature, the pilot gas ignites and heats up the thermostatic bulb 23causing the bellows 24 toexpand opening switch members 31 and 38 andclosin 39. Thus the igniter is deenergized and the motor I4 is energizedopening the main burner valve. Fuel entering the main burner is thenignited by the pilot burner.

When the control switch or thermostat 20 opens, it deenergizes motors l8and I4 closin valves l1 and I3 which turn oil the gas supply to both themain and pilot burners. Pressure switch 43 then opens due to the drop offuel pressure in conduit l6 and finally when the thermostatic bulb 23has cooled sufilciently, switch members 31 and 38 close and 39"opens.This completes a cycle of operation.

Because of the time required for the combustion responsiv device 22 tooperate it is necessary to protect against abnormal conditions of 1operation such as voltage and fuel p7 -Jsure dips bumed fuel wouldescape from the main burner until combustion responsive device 22 couldreturn to the start position and energize the ig- The ignition then of alarge quantity The closing ofthe pilot burner age dip which causes thepilot valve ll to close,

because of deenergization of its control motor l3, will drop the gaspressure in conduit 16 sufficiently to open pressure switch 43. Returnof voltage to normal cannot then re-open the pilot or main valve untilthe combustion responsive device 22 returns to the start position andcloses switch member 31 to recycle the operation of the control system.Manual operation of the switch 20, which produces the effect of avoltage dip is also protected against in' a similar manner.

Likewise a pressure dip of suflicient magnitude to put out the pilotwill open pressure switch 43. This will result in closure of the mainand pilot burner valves and upon a rise in pressure of the fuel nounburned gas can escape until the recycling operation is completed. Thusthe provision of a single operating means, namely, the pressure operatedswitch 43, operates to give protection against both supply voltage andfuel pressure failure.

Also it is evident if during th starting operation the pilot rails toignite for some reason P main open upon a closure of control switch 20but the amount of unburned fuel escaping from the pilot is so small thatno dangerous condition is likely to result.

While I have shown and described a specifi I embodiment of my invention,it will become apparent to those skilled in the art that my inventionhas other applications, and that changes and modifications may be madewithout departing from the spirit and scope of my invention. Lthereforeaim in the appended claims to cover all such modifications and changes.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In afluid fuel burner control system, a main burner connected to afuel supply source by a main burner conduit, a normally closed valveinterposed in said main burner conduit, a pilot burner connected to saidfuel supply source by a pilot conduit, a normally closed pilot valveinterposed in said pilot conduit, electrically actuated opening meansfor the burner valve, electrically actuated opening means for the pilotvalve, means for igniting the pilot burner, an energizing circuit forthe main valve and pilot valve opening means, a first switch in saidenergizing circuit, a second switch for controlling the energization ofsaid main valve opening means, heat responsive means associated withsaid pilot burner for controlling said first and second switches, saidheat responsive means being normally at a start position in which saidfirst switch is closed and said second switch is open and moving to arun position in which said first switch is open and said second switchis closed in response to combustion at the pilot burner, a holdingcircuit shunting said first switch, said holding circuitincluding anormally open pressure switch and means for closing said pressure switchupon the attainment of a predetermined fuel supply pressure in the pilotconduit between the pilot valve and the pilot burner whereby upon afalling of said pressure below said predetermined value when said heatresponsive means is in the run position and said first switch is open,said pressure switch opens causing a deenergization of the main andpilot valve opening means and a closureofthe main and pilot valves sothat said pressure switch cannot reclose until said heatresponsive'means returns to the start position to close said firstswitch and reopen said pilot valve.

2. In a fluid fuel burner control system, a main burner connected to afuel supply source by a main burner conduit, a normally closed valve.interposed in said main 'bumerconduit. a pilot burner connected to saidfuel supply source by ated opening means for the burner valve,electrically actuated opening means for the pilot valve, means forigniting said pilot burner, aswitching device having a set of normallyopen and a set of normally closed contacts, means dependent on theoccurrence of combustion at said pilot burner for actuating saidswitching device to close said normally open contacts and to open saidnormally closed contacts, a normally open pressure switch, means forclosing said pressure switch upon attainment of a predetermined pressurein the pilot conduit between said pilot valve and said pilot burner, anenergizing circuit to which said pilot valve opening means is connected,said energizing circuit having a portion comprising two parallel paths,one of said paths including the normally closed contacts of saidswitching device and the other of said paths including said pressureswitch, said main burner opening means being connected in parallel withsaid pilot burner actuating means by a circuit including the normallyopen contacts of said switching device.

3. In a fluid fuel burner control system, a m burner connected to a fuelsupply source by a main burner conduit, a normally closed valve--interposed in said main burner conduit, a pilot burner connected tosaid fuel supply source by I a pilot conduit, a normally closed ilotvalve interposed in said pilot conduit, electrically actu-' ated openingmeans for the burner valve, elecpilot burner for-actuating saidswitching device to close said normally open contacts a'ndto open saidfirst and second normally closed contacts, a normally open pressureswitch, means for closing said pressure switch on the attainment of apredetermined pressure in the pilot conduit between the pilot valve andthe pilot burner, an

energizing circuit to which said pilot valve opening means is connected,said energizing circuit having a portion comprising two parallel paths,one of said paths including the first normally closed contacts of saidswitching device and the other of said paths including said pressureswitch,

said main burner opening means being connected in parallel with saidpilot burner opening means by a circuit ,.including-the, normally opencon tacts of said switching device and said electrically operatedigniter being connected in parallel with said pilotburner opening meansby a circuit including the second normally closed contacts of saidswitching device.

4. In a fluid fuel burner control system, a fuel burner, a conduitinterconnecting said burner and a source of fuel supply, a normallyclosed valve interposed in said conduit, electrically actuated means foropening said valve, an energizing circuit for said valve actuatingmeans, a first switch in said energizing circuit, a holding circuitshunting said first switch, said holding circuit including a secondswitch, means for operating said second switch in accordance with thefuel pressure in the conduit between said valve and said burner,igniting means for said burner, and means responsive to combustion atsaid switch.

burner for controlling said igniting means and said first switch.

5. In a fluid iuel burner control system, a fuel burner, a conduitinterconnecting said burner and a source of fuel supply, a normallyclosed valve interposed in said conduit, electrically actuated means foropening said valve, an energizing circuit for said valve actuatingmeans, a first switch in said energizing circuit, a holding circuitshuntlng'said first switch, said holding circuit including a secondswitch, means for operating said second switch in accordance with thefuel pressure in the conduit between said valve and said burner, andmeans responsive to combustion at said burner for controlling said firstssmim. J. LEVINE.

